Electric frequency separator



Dec. 31, 1940. WIESSNER 2,227,384

ELECTRIC FREQUENCY SEPARATOR Filed July 10, 1937 Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE ELECTRIC FREQUENCY SEPAHATOR Application July 10, 1937, Serial No. 153,073 In Germany September 7, 1936 1 Claim.

It is well known to transmit high frequency communications over a network which at the same time serves for the transmission of low frequency communications. For instance, high frequency carrier waves are impressed upon a telephone network in order to serve for the transmission of amusement or alarm communications or signals. In arrangements of this kind low frequency and high frequency must be separated from each other or brought together, as the case may be, by so-called separating filters. One such,

filter is disposed in the subscribers station and may therefore be designated as subscribers filter and another is disposed in the exchange station or office, and hence may be designated as office filter.

The filters consist of a high-pass filter and a low-passfilter. These are made up of inductances and capacities. The low-pass filter comprises inductances included in the line wires and also comprises condensers for short-circuiting these wires in high frequency fashion. The highpass filter is composed of capacities located in the line wires and of inductances disposed between these. It has been proposed to use the low-pass filter at the same time for suppressing disturbing oscillations that arise in the low frequency portion of such an arrangement in both phase coincidence and phase opposition,

Such filters should be of the smallest possible place requirements, because in the exchange stations, for instance, many separating filters must be arranged side by side in order to impress the high frequency on the low frequency wires. It

is most difiicult however so to arrange the inductances within the smallest possible area that no detrimental coupling effects shall arise.

In accordance withthe invention these difliculties are overcome by enclosing the inductances with a shell of high frequency iron and fixing them on a spindle which is common to these inductances.

The invention will be understood from the following description, reference being had to the accompanying drawing in which Fig. 1 is a partially-sectioned view of an arrangement chosen as an example. Fig. 2 shows a section on line 2-2 of Fig. 11. Fig. 3 is the wiring diagram of a separating filter of known construction. Fig. 4 represents a longitudinal section of a second example of the novel arrangement. "Fig. 5 shows a section on line 5-5 of Fig. 4.

On a spindle I, Figs. 1 and 2, three inductances 5 2, 3, 4 are fixed which may in a suitable manner be used for assembling frequency separators. These inductances comprise windings p which are each enclosed with a shell q of high frequency iron. The shells q are joined to the cores 1' of the inductances by discs s. The discs 5 s and cores 1* likewise are of high frequency iron. Spindle I and thus the inductances mounted on it are fixed in an U-shaped frame 9, for instance, which also carries the condensers ID. This arrangement is contained in a screening case II and thus can be employed for assembling separating filters in a simple manner. Such a filter is shown in Fig. 3.

In the arrangement represented in Fig. 3 high frequency and at the same time low frequency 15 communications are conveyed to a subscribers station over the wires or, b, these two kinds of communications being segregated by the separating filter. This consists of a low-pass filter A and a high-pass filter B. The low-pass filter A here shown by way of example comprises an H-shaped member, composed of four inductances 2, 3, 4, 4' and two condensers I0 earthed at their center point in order to provide for suppressing 25 the disturbing oscillations which arise in the low frequency portion A. The high-pass filter B comprises four condensers I0, two inductances 6, I and a high frequency transformer 8 which serves to lead away the high frequency communi- 30 cations.

The inductances 2, 3, 4, 4' are according to Figs. 4 and 5 disposed on a spindle I and are fitted with shells q of high frequency iron so that the windings 12 thereof are located in these shells. 35 The inductances 2, 3 have each a core 1' of high frequency iron. The inductances 4, 4' have both one common core 1- likewise of high frequency iron. The inductances 6, I are mounted on a second spindle 5 and like the inductances 2, 3 40 have each a high frequency iron core T. On spindle 5 also transformer 8 is mounted which is likewise surrounded with a shell q of high frequency iron. The shells q and cores r are interconnected by discs s of high frequency iron. The 45 spindles I, 5 are interconnected by a frame 9 to which also the condensers ID are fixed in a suitable manner, as by supports I3. The condensers are in this way located between the inductances 2, 3, 4, 4 of the low frequency portion and the 50 inductances 6, I of the high frequency portion. The windings t are connected to the condensers If! by leads I2 in the manner, for instance, shown in Figs. 3 and 4. The parts 2, 3, 4, 4', 6, I, 8, II] may however be interconnected in any other suitable or desired manner. a screening case.

The shells q act to concentrate the lines of force so as to prevent them from straying.

The arrangement is adapted for use in both subscribers stations and exchange stations and is adapted also to suppress disturbing oscillations that seek to arise in the low frequency portion.

What is claimed is:

An electric filter for separating high frequency currents from low frequency currents including a pair of input terminals for connection to a line, a pair of output terminals for connection to a line, a first set of two closely coupled inductances, a second set of two inductances ma netically isolated from each other, a common core of high frequency iron for the first set of inductances and a high frequency iron shell enclosing said first set of inductances and forming l I also here denotes pairs of terminals, and from one end of each of said two isolated inductances to the other of said pairs of terminals, and from the other ends of said two closely coupled inductances to the other ends of two isolated inductances, respectively, and condensers connected between said other ends of all said inductances to ground.

ALFRED WIESSNER. 

